Dear Jaison, Thanks for your response, it is solved now. Then another question : is it possible to overlay buoy location with an oceanographic field, like temperature for example, without any interpolation to put the scattered data onto a grid (see image attached) ? Best regards, Tony PS : Jaison, my error was : first there was 2 buoys in my file, so the time was not, momotonic, and second I didn't know the "set pecision" so I searched on a wrong way to solve my problem. Thanks a lot. Jaison Kurian wrote: Hi Tony & Ansley, I think Ferret is right in this case. For the given subset of your data Ferret makes a time axis within the error of 1 seconds. Few corrections to your script : LET days_2001 = DAYS1900(2002,1,1) ==> T0 should be 1-jan-2002 ( not 1-jan-2001) If FILE command doesn't have the /grid=gridname qualifier it will read the variable on to X-axis/grid (try listing tstep). So "tstep[L=1:50]" is meaningless ; "tstep" is good enough. test.dat -------- [5] 2002-07-28 13:59:50 09435 28700 NM T 2 48.989 339.229 [5] 2002-07-28 14:37:53 09435 28700 NH T 2 48.987 339.230 [5] 2002-07-28 15:13:44 09435 28700 NL T 3 48.989 339.245 [5] 2002-07-28 16:05:40 09435 28700 ND T 1 48.988 339.252 [5] 2002-07-28 16:56:52 09435 28700 NL T 1 48.989 339.269 [5] 2002-07-28 17:40:02 09435 28700 NJ T 3 48.996 339.281 [5] 2002-07-28 19:18:48 09435 28700 NJ T 2 48.995 339.318 [5] 2002-07-28 19:29:02 09435 28700 NK T 1 48.999 339.343 test.jnl -------- FILE/SKIP=0/FORMAT=delim/delimiter="\b"/type="text,date,time" test.dat LET days_2001 = DAYS1900(2002,1,1) LET day_frac = v3/24 LET tstep = v2 - days_2001 + day_frac DEFINE axis/T/T0=1-jan-2002/UNIT=days ttaxis=tstep set list/precision=7 ! <== to see up to 4 deci. places list t[gt=ttaxis] .................. VARIABLE : T axis TTAXIS SUBSET : 8 points (TIME) 28-JUL-2002 13:59:50 / 1: 208.5832 28-JUL-2002 14:37:52 / 2: 208.6096 28-JUL-2002 15:13:43 / 3: 208.6345 28-JUL-2002 16:05:40 / 4: 208.6706 28-JUL-2002 16:56:52 / 5: 208.7062 28-JUL-2002 17:40:01 / 6: 208.7361 28-JUL-2002 19:18:47 / 7: 208.8047 28-JUL-2002 19:29:01 / 8: 208.8118 Please note that the error is of the order of 1 second only. For this subset of your actual data, Ferret is doing a good job. Please check the remaining portion of your data for decreasing values (say from 9th line to 50th line). There will be at least one line of data with values for hr/min/sec less than the previous line with respect to the date. Try to see the values of tstep after increasing the list precision. Hope this helps With Regards Jaison On Wed, 27 Oct 2004, Tony Jolibois wrote:Hi Ansley, Excuse me I didn't send details. Here it is : The data contains year, month, day, hour-minute-second, location and other things : buoy.dat : [5] 2002-07-28 13:59:50 09435 28700 NM T 2 48.989 339.229 [5] 2002-07-28 14:37:53 09435 28700 NH T 2 48.987 339.230 [5] 2002-07-28 15:13:44 09435 28700 NL T 3 48.989 339.245 [5] 2002-07-28 16:05:40 09435 28700 ND T 1 48.988 339.252 [5] 2002-07-28 16:56:52 09435 28700 NL T 1 48.989 339.269 [5] 2002-07-28 17:40:02 09435 28700 NJ T 3 48.996 339.281 [5] 2002-07-28 19:18:48 09435 28700 NJ T 2 48.995 339.318 [5] 2002-07-28 19:29:02 09435 28700 NK T 1 48.999 339.343 --------- time ---------- lat lon Here is the script I tried to create the time axis : FILE/FORMAT=delim/delimiter="\b,\t"/type="text,date,time,numeric,numeric,text,text,numeric,latitude,longitude"/EZ bouee_28700-32790.txt LET days_2001 = DAYS1900(2002,1,1) LET day_frac = v3/24 LET tstep = v2 - days_2001 + day_frac list tstep 1 / 1: 175.7 2 / 2: 175.7 3 / 3: 175.7 4 / 4: 175.7 5 / 5: 175.8 6 / 6: 175.8 7 / 7: 175.9 8 / 8: 175.9 ... So you can see that when I try to create the time axis, ferret says DEFINE axis/T/T0=1-jan-2001/UNIT=days ttaxis=tstep[L=1:50] **ERROR: improper grid or axis definition: data for DEFINE AXIS/FROM_VARIABLE is not monotonic Thanks for your response, Tony 2002-07-28 13:59:50 Ansley Manke wrote:Hi Tony, What are your timestps like? Units of seconds over the course of a month? Or what? Are they regularly spaced or irregular? Ansley Manke Tony Jolibois wrote:Hi ferreters, I'm trying to plot Argos buoy location with a time axis. The data are in ascii file, so I read this page to create my time axis : http://ferret.pmel.noaa.gov/Ferret/FAQ/axes_and_data/time_axis_from_variables.html. In the end of the page, you can find that : Note that Ferret variables are represented as single precision real numbers. (Axes are represented in double precision, but we are using a variable to define the axis and that variable is single precision.) If your timestep is small, such as minutes, and your times are a century or more after 1-jan-1900, you will need to use a time origin later than 1-Jan-1900 The problem is that my timestep is so small that enven if I use a new time origin some step which was not equal are equal after the calculation. Can someone know how can I define a variable with a better precision, or tell me what can I do to define a good time axis ? Thanks in advance, Tony |